About what Stick said. The SCMS has pretty much replaced it. They were never particularly accurate. The most common use was on construction sites for repetitive cut off as in when cutting cross bracing for floor joists. You had to be pretty careful when using them not to put torque on the handle or you would pull them off square.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.